PREFACE BY DENIS McCORMACK

Society of Automotive Engineers


| September/October 1967



Cartwright's Engine

Denis McCormack

I am the fortunate possessor of an original copy of Elijah Galloway's 'History and Progress of the Steam Engine', published in London in 1831.

Written as it was by an engineer - himself an inventor of several early steam engine designs, at a time when the great development of the steam engine and its adaptation to ships, railway locomotives, road vehicles and innumerable industrial applications was actually taking place, Galloway's book, despite its somewhat stilted English of 136 years ago, vibrates with the zeal and the excitement of an engineer partaking, observing and recording the great engineering developments of that period.

I would like to share the pleasure I have had in the reading and I shall be happy to furnish further extracts and illustrations that trace some of the fundamental forward moves which gave such great stimulation to modern progress.

Cartwright's Patented Steam Engine of 1797

'The Rev. Edward Cartwright's scheme for which he obtained a patent in 1797, was very ingenious. His object was to produce a tight piston, and a condenser in which the steam was exposed to a large surface of water.

The condensation is effected by two metal cylinders, placed one within the other, and having cold water flowing through the inner one, and inclosing the outer one. Thus the steam is exposed to the greatest possible surface in a thin sheet. Mr. Cartwright likewise has a valve in the piston by which a constant communication is kept up between the cylinder and condenser, on either side of the piston; so that any steam improperly entering the cylinder, is instantly exposed to the condenser, whether in the ascending or descending stroke. By this contrivance, steam that may escape past the piston will be immediately condensed, and the vacuum thereby preserved. This was considered to be a decided advantage over the general mode of arranging the valves, which does not always provide for the restoration of a vacuum destroyed by the imperfection of the packing.

In the following figure, the piston b moving in the cylinder a, has its rod prolonged downwards; another piston d is attached t o it, moving in the cylinder c, and which may be also considered as a prolongation of the steam cylinder. The steam cylinder is attached by the pipe g to the condenser, placed in cold water, formed of two concentric circular vessels, between which the steam is admitted in a thin sheet, and is condensed by coming in contact with the cold sides of the condensing vessel. The water of condensation falls into the pipe e. To the bottom of the cylinder i, a pipe m is carried into a box n, having a floatball o, which opens and shuts the valve p, communicating with the atmosphere: a pipe q is also fitted to the box. There is a valve placed at i, opening into the cylinder c; another at n, also opening upwards. The pipe s conveys steam from the boiler into the cylinder, which may be shut by the fall of the clack r. k is a valve made in the piston b.